Conventionally, a plasma processing apparatus for performing various processes, e.g., etching, film formation and the like, on a substrate (e.g., a semiconductor wafer) provided in a processing chamber by using a plasma has been used in a semiconductor device manufacturing process.
As for the plasma processing apparatus, there is known, e.g., a capacitively coupled plasma processing apparatus for generating a plasma by applying a high frequency power between a lower electrode also serving as a mounting table (susceptor) for mounting thereon a semiconductor wafer and an upper electrode disposed to face the lower electrode. Further, in this plasma processing apparatus, it is known that an electrostatic chuck for electrostatically attracting a semiconductor wafer is provided at the lower electrode and an annular focus ring is disposed to surround the semiconductor wafer, thereby improving processing uniformity (see, e.g., Japanese Patent Application Publication No. 2008-306212).
In this plasma processing apparatus, a bias voltage of about −2000 V at maximum is generated at the focus ring and the semiconductor wafer exposed to the plasma. Meanwhile, a plus voltage of about 2000 V to 2500 V is applied to the electrode of the electrostatic chuck, so that polarization charges are generated between the electrode of the electrostatic chuck and the base of the lower electrode which is made of a conductive metal. In this case, a polarization potential is divided by a high frequency application circuit connected to the base of the lower electrode and becomes about 2000 V at maximum while it is determined by a high frequency application circuit constant and a chamber circuit constant.
Therefore, a potential difference of about 4000 V at maximum is generated between the semiconductor wafer and the lower electrode. This leads to discharge (arc) between the semiconductor wafer and the base of the lower electrode or its surrounding structure, so that semiconductor chips formed on the semiconductor wafer may be damaged. When the semiconductor chips formed on the semiconductor wafer are damaged, a production yield is decreased and, also, productivity is decreased.
The discharge can be prevented by increasing a withstand voltage between the semiconductor wafer and the base of the lower electrode or the like to, e.g., about 5000 V. However, it is not easy to increase the withstand voltage because the lower electrode is provided with, e.g., openings for lift pins for lifting the semiconductor wafer, gas supply openings for supplying He gas for transferring heat between the backside of the semiconductor wafer and the surface of the electrostatic chuck and the like.